1. Field
This disclosure relates to solid fuel rocket motors, and to fast response motors suitable for use as attitude control thrusters.
2. Description of the Related Art
Solid fuel rocket motors are commonly used in various configurations to propel rockets and missiles. Small solid fuel rocket motors may also be used to control the attitude and steering of a missile, rocket, or other projectile. Small solid fuel rocket motors used to control attitude are commonly called attitude thrusters or divert thrusters. Solid fuel rocket motors may also be used to turn a vertically-launched missile or rocket into near-horizontal flight. Such rocket motors are commonly called pitch-over thrusters.
The thrust or force produced by a rocket motor is given by the equationF=mp*Ue+(Pe−Pa)*Ae                 where                    mp=propellant mass flow rate, and            Pe=Nozzle exit pressure            Pa=Ambient pressure            Ae=Nozzle exit area            Ue=gas velocity at nozzle exit plane.                        
When a rocket motor includes an ideally expanded nozzle, Pe=Pa, and the equation for the thrust produced by the rocket motor reduces toF=mp*Ue.
The propellant mass flow rate mp is given by the equationmp=Ap*Rb*Pp                 where                    Ap=propellant surface area,            Rb=propellant burn rate, and            Pp=propellant density.                        
Thus the propellant surface area Ap, the propellant burn rate Rb and the propellant density Pp are important factors that may be used to determine the thrust produced by a solid fuel rocket.
The force produced by a rocket motor results in a linear or angular acceleration of the missile or other body propelled by the rocket motor. The net change in the linear or angular velocity of the missile or other body is proportional to the force produced by the motor integrated over time. The time integral of the force produced by a rocket motor is commonly called the “impulse” of the motor.
Divert thrusters and other solid fuel rocket motors may provide a single impulse or may be configured to provide multiple impulses by consecutively burning multiple propellant charges. A typical multiple-impulse rocket motor, such as that shown in U.S. Pat. No. 5,160,070 for example, may include a plurality of propellant charges arranged in sequence in a common case. Each of the plurality of propellant charges may have a separate igniter. Each of the plurality of propellant charges may be separated from the adjacent propellant charges by a burst disk or other barrier. The plurality of propellant charges may be ignited in sequence starting with the propellant charge disposed adjacent to a nozzle.
Throughout this description, elements appearing in figures are assigned three-digit reference designators, where the most significant digit is the figure number and the two least significant digits are specific to the element. An element that is not described in conjunction with a figure may be presumed to have the same characteristics and function as a previously-described element having a reference designator with the same least significant digits.